1. Field of the Invention
This invention relates to the general field of bits for earth and rock drills, and in particular, to an improved rotary percussion bit.
2. Prior Art
Rock bits known in the art, particularly rotary percussion bits, are known to have particularly complex geometrical configurations which do not lend themselves to inexpensive or simple production. Some rock bits are also provided with means for replacing individual cutting elements which have become worn or broken through usage. With respect to the prior art, a rock bit according to this invention provides simple geometry, ease of construction and a relatively simple arrangement for replacing cutting elements.
The simple, but unique geometry of this invention is apparent from its basic structure, a round, plate-like member. All of the cutting elements are secured to a substantially flat surface. Although some bits are known in which cutting elements are mounted to a substantially flat surface, this invention is radically different with respect to the manner in which the cutting elements are mounted.
Cutting elements are frequently pressed or brazed into the bit. These are difficult to repair or replace by the nature of their attachment. Removable cutting element assemblies have been provided, such assemblies having a replaceable cutting element supported in a bit recess with a split sleeve. The recess has a space behind the sleeve and the cutting element with an anvil member located therein to prevent further penetration of the cutting element, but which enables the sleeve to be pushed further into the recess to release the cutting element when a force of sufficient magnitude is supplied thereto. Neither of these methods is particularly satisfactory. By way of contrast, a bit according to this invention is provided with a plurality of raised sections, relatively distributed on one surface of the basic plate-like member. These raised sections are formed from rings, which are secured to the surface of the plate-like member and filled with a filler material such as welding rod. A plurality of carbide cutting elements are mounted in each raised section of filler material. The surface of the plate-like member is therefore covered by a plurality of cutting elements disposed therein. Mounting the cutting elements in a filler material such as welding rod provides both secure attachment and a relatively easy means for replacing the cutting elements. No machining or press fitting is required. The bit is further provided with a plurality of air or exhaust holes and a plurality of projecting ribs mounted around the rim of the plate-like member.
With respect to ease of construction, no specially contoured, beveled or grooved shapes must be machined in order to produce a rock bit according to this invention.